Front-end loaders are popular additions to compact utility tractors and larger farm tractors. Compact Utility Tractors (CUT) are small tractors typically having 18 to 50 horsepower, and are often used to perform grounds maintenance, landscaping, and farming tasks. Most commonly these tractors are 2-wheel drive, although some CUTs are 4-wheel drive. Typically, front-end loaders include two booms, each boom being either a traditional “dogleg” style, or a curved arm style.
Front-end loaders on compact utility tractors are capable of many tasks and can include many optional accessories. For example, bucket accessories are commonly used to move dirt, sand, and gravel from one area to another, and a tooth bar accessory can be added to the front edge of the bucket to aid with digging. Some front-end loaders are equipped with a quick coupler, otherwise known as a quick attach system. The quick attach system allows accessories, such as the bucket, to be removed easily and then allows another accessory to be quickly attached. Other common accessories include pallet forks for lifting pallets of goods, or bale spears for lifting bales of hay or other soft materials.
In the agricultural industry, as well as in the construction industry, the majority of front-end loaders that are attached to a compact utility tractor or a farm tractor are of the same structure. Typically, the front-end loader includes two booms, each boom being an obtuse angled “dogleg” boom that has a fixed, hinged point of attachment that serves as a load bearing base. The two booms are usually made of tubular boxed steel, and included is a “cross piece” toward the front of the assembly that holds the two booms together at a fixed distance with respect to each other.
Working on materials located at the ground level immediately in front of the tractor is a very common work application for front-end loaders. An example of this application would be using a front-end loader bucket accessory to scoop up gravel from a pile of gravel located immediately in front of the tractor. To manipulate materials at ground level immediately in front of the tractor, the booms must be lowered to a position where the front ends of the booms are near, or are at, the ground level.
To accomplish lowering the accessory to ground level, traditionally each boom has a “dogleg” obtuse angular bend of 105 to 135 degrees. This “dogleg” bend prevents the booms, when in the lowered position, from striking against the front wheels of the tractor, or from striking against other parts of the tractor, such as the front fenders. The “dogleg” bend allows the booms to arch over the tractor wheel areas and to extend down to the ground area in front of the tractor, allowing an accessory, such as a bucket, to work at the ground level immediately in front of the tractor.
In addition, the “dogleg” bend in each boom allows the accessory, such as the bucket or the bale spears, to place the payload onto the truck or the wagon without the underside of the booms striking against the side of the truck or against parts of the wagon.
The “dogleg” bend in each boom is located midway between the hinged point of attachment of the boom to the tractor at the load bearing base, and the traveling end of the boom where the bucket (or other accessory) is mounted to the boom.
In recent years, to add a “stylish” or “streamlined” look to their products, some loader manufacturers have replaced the obtuse dogleg angle in the midsection of the boom with a gentle continuous arc bend that runs from one end of the boom to the other end. Nevertheless, this continuous arc bend accomplishes the same objectives as an obtuse 105 degree to 135 degree dogleg bend—namely, to arch over the front wheel areas of the tractor, while still having the front ends of the booms extend to reach the ground level immediately in front of the tractor.
Many front-end loaders have a self-leveling option that includes a mechanical linkage that maintains the bucket (or any attachment that replaces the bucket) at a constant tilt angle as the booms are raised and lowered. As the height of the bucket is changed, the self-leveling linkage keeps the bucket accessory at the same tilt angle. Accordingly, this type of front-end loader is called a self-leveling front-end loader.
Front-end loaders mounted on compact utility tractors are traditionally used to load material on a truck such as a dump truck, and lift bales of hay or other materials onto a flatbed truck or a hay wagon. Unfortunately, the terrain of the construction/work site and/or the height of the truck may prevent the front-end loader from effectively reaching the height of the truck so that the material can be placed on the truck (or wagon). In addition, if the front-end loader attempts to lift and place a bale on top of other bales that have already been placed on the truck, the front-end loader booms may not have adequate reach to lift and place the bale at such a high position.
In an effort to address this issue of inadequate boom length, a commercially available telescopic front-end loader is sold by Kishan Equipment of Rajkot, India (www.kishanloader.com) for use in the cotton industry. This front-end loader has a double boom configuration, with each boom being extendable by hydraulic power to increase the boom length, and therefore extend the reach of the loader. However, the two booms are of a straight design, and therefore do not have the 105 to 135 degree angle that is typical of a common front end loader. Because the booms are straight and have no bend, this design cannot be used to manipulate materials immediately in front of the tractor, since when lowered, the straight booms would not be able to reach ground level without striking the front wheels of the tractor. The wheels therefore prevent the straight booms from reaching the ground level immediately in front of the tractor.
Also, this front-end loader of Kishan Equipment of India has booms that extend outward approximately from 7 to 17 feet in front of the tractor. Extending the booms to such a great length reduces the stability and lifting capacity of the entire machine. In addition, the substantial weight of the booms, combined with the large forward boom extension length, add a large tilting force to the tractor. To compensate for the large tilting force of the long booms, the tractor must include a large compensating rear counterweight that is mounted on the back of the tractor. However, the mounting of the large rear counterweight on the tractor eliminates the availability of the tractor's rear draw bar and rear power lift, and the rear placement of the large weight makes the mounting of any rear accessories impossible. This greatly reduces application of this machine to handling only lightweight materials, and prevents the tractor from having any rear accessory tools.